Obese more likely to die of cancer

What a devastating experience it must have been for Elizabeth Edwards, wife of the former U.S. vice-presidential candidate John Edwards, to be told on the day of his loss, after spending two gruelling years campaigning with him, that she had breast cancer. This was more than enough bad news for one day. Unfortunately for both sexes obesity increases the risk of many malignancies.

Dr. Penny Anderson, a cancer specialist at the Fox Chase Cancer Center in Philadelphia, reports that obese breast cancer patients are more likely to die than normal weight women. Yet another blow for Elizabeth Edwards who spoke candidly during the campaign about her struggles to control weight.

Dr. Anderson and her colleagues studied 2010 women who had been treated by lumpectomy, radiation therapy with or without chemotherapy for breast cancer. Based on their weight, they were divided into three groups, normal weight, overweight and obese.

After five years, 92% of the normal weight women had survived. But the survival rate was only 88% for those who were obese. Moreover, obese women were more likely to have developed recurrent cancers.

So why is obesity such a risk factor for breast cancer? Dr. Eleanor Harris, assistant professor of Oncology at the University of Pennsylvania, suggests that it's due to increased amounts of the female hormone, estrogen.

Prior to menopause, estrogen is produced primarily by the ovaries. But following menopause, the main source is from fatty tissue. The greater the obesity the higher the level of estrogen. It's been shown that estrogen levels in post-menopausal women are 50% to 100% higher in obese versus lean women. And abdominal fat is a greater risk factor than fat distributed over the thighs, buttocks and legs.

Another explanation is that obese women, who are also more likely to have heart and/or kidney disease, are less able to tolerate chemotherapy. And that small breast lumps are more difficult to detect in heavy women.

But if obese males think they're immune to this increased risk of cancer they had better think again. The National Cancer Institute reports that an increased risk of colon cancer has been consistently reported for overweight males.

The Journal of Clinical Oncology adds that obese men with prostate cancer are more likely to have aggressive tumours. In addition, they experience cancer recurrence more often following surgery than men of normal weight. This is particularly true of African-American males who tend to be more obese than Caucasian men.

Researchers suggest that proteins and hormones stored in body fat may promote cancer growth in obese males. Overweight males also have lower levels of the male hormone testosterone and higher levels of estrogen which are believed to encourage the growth of cancer.

Obese individuals of both sexes are also two times more likely to develop esophageal (food pipe) and stomach cancers. It's not understood why this happens. Some speculate that it may be related to gastric reflux (heartburn) that occurs more often in overweight individuals.

GALLBLADDER, PANCREAS

In a huge study involving 900,000 people for 16 years Harvard researchers concluded that 14% of cancer deaths in men and 20% in women were caused by being overweight. For several years it's been known that obese people face a greater risk of developing cancer of the gallbladder and pancreas. And overweight women have two to four times the risk of uterine cancer than women of a healthy weight.

These reports are not happy news for Elizabeth Edwards and others who are overweight. It's also known and depressing that aging also increases the risk of breast, prostate and many other malignancies. Obesity and aging is a bad combination for developing cancer.

I prefer to end these columns with hope of solution, but this one presents difficulties. A famous economist remarked: "In the long run we are all dead." Since getting older is invariably fatal, and we can do nothing about it, this leaves us with the great imponderable, how to fight the current epidemic of obesity. This would require Draconian measures, not acceptable by many, so we will see more obese patients diagnosed with cancer. I prefer happier endings, but I wish Elizabeth Edwards a return to good health.